Right now, it's just a prototype, or perhaps it can be called a half-move. Casio has yet to perfect it, and it has a sizable flaws.
It should not have been used in a sparring match at the ranks of fighters, but Casio, entrenched in a murderous personality, was naturally arrogant and audacious, and utterly fearless. Coupled with the previous bout of contact with this murderous persona, he felt that his opponent was not as strong as he is.
Thus, he used his half-formed move directly in battle.
The best way to test whether a killing move and secret technique are useful or not is through combat, which can instantly reveal any shortcomings.
Casio dared to do what others didn't dare to do due to his extraordinary healing abilities provided by the Secret Martial Art of the Demon Idol.
Hiss, hiss, hiss!
